1. Field of the Invention
The present invention relates in general to a seat belt retractor, and more particularly to a seat belt retractor with an electronically controlled tensionless mechanism.
2. Description of a Prior Art
Japanese Patent Application Second Provisional Publication No. 52-9891 shows a conventional seat belt retractor with an electrical controlled tensionless mechanism. In the known retractor, an electric motor is operated just after a seat occupant has worn a seat belt so as to rotate a belt take-up shaft in a belt feeding direction by a predetermined amount of slack. This known retractor, however, has a drawback that since once the tensionless state is established, the belt take-up shaft is locked and thus prevented from rotating in the belt feeding direction, the belt can not be pulled out of the retractor further, thus restraining the seat occupant from changing his or her sitting posture. This becomes much severer when the driver wearing the belt intends to turn back for driving the vehicle in reverse. That is, upon such requirement, the driver has to switch OFF the electric controller for releasing the tensionless state of the seat belt. However, the switch OFF manipulation is troublesome and the driver must carry out the reverse driving while feeling uncomfortable tension applied to him or her by the seat belt.